The present invention relates to an apparatus for ventilating the crankcase of a combustion engine, comprising a vent line running from the crankcase to an intake pipe of the combustion engine and an oil-mist separator that is arranged in the course of the vent line.
An apparatus of the said type is known from the practice of engine construction, in particular for automobiles. This apparatus aims at maintaining in the crankcase of the combustion engine a vacuum pressure that is required for technical and legal reasons by ventilating the crankcase; to achieve this, gases or, in particular, blow-by gases are conducted out of the crankcase or the combustion chambers of the combustion engine to the intake pipe of the engine. Any oil contents carried in the crankcase ventilation gas are separated in an oil-mist separator; preferably, the separated oil is supplied to the lubricating oil circuit of the combustion engine again. The gas that has been freed from the oil enters the intake pipe of the combustion engine and is then running through the combustion that takes place in the engine.
Known apparatuses of the said type have various operational drawbacks that are, in particular, incurred in certain operating states. A drawback of spark-ignition engines is that the drop in pressure above the oil-mist separator is relatively high and causes the danger of an excess pressure developing in the crankcase if the difference between the vacuum pressure in the intake pipe and the atmospheric pressure is inadequate. Moreover, this results in a reduced efficiency of the oil-mist separator because in spark-ignition engines, use is normally made of separators that are operated by the principle of inertia and require a high efficiency to ensure an adequately high volume flow. Another drawback is incurred whenever the combustion engine is in its no-load range because, in this state, the pressure developing in the crankcase may become too high. This problem is, in particular, arising in case of advanced combustion engine wear because this may lead to high blow-by volume flows at high speed and no-load.
For that reason, the present invention aims at creating an apparatus of the aforementioned type, which obviates the drawbacks disclosed and which, in particular, permits to maintain a vacuum pressure in the crankcase of the combustion engine in any and all possible operating states of the combustion engine, with the vacuum pressure being negative in comparison with the atmospheric pressure, and, at the same time, to ensure a high efficiency of the oil-mist separator.